Partial discharge is caused by the localised electrical breakdown of electric insulation materials under high voltage stress. Detecting and measuring partial discharge events is a useful way of identifying underlying electrical breakdown and other incipient faults in electrical apparatus.
Existing methods of detecting partial discharge events involve the use of sensors on the apparatus being monitored to detect electrical pulses caused by a partial discharge event. Suitable sensors include coupling capacitors and inductive high frequency high current transformers. Transient earth voltage detectors have been employed to sense the electromagnetic field at gaps in the metal enclosures of switchgear so as to detect partial discharge events in the switchgear.
In each case the sensor must be placed near to the apparatus being monitored so as to detect discharge events originating from the apparatus.
Often electrical machines operate in remote and dangerous environments. An example is in oil and gas installations where electric motors used to drive pumps and compressors are located a considerable distance from switchgear that controls the motor, and may be located in an explosion risk environment. Monitoring electrical apparatus at multiple remote locations involves installing suitable sensors on each item of apparatus and arranging for the sensor outputs to be relayed to a convenient monitoring point. Where the apparatus is in an explosive risk environment it is subject to strict safety criteria and any associated monitoring equipment must also meet that criteria. These requirements are onerous and consequently monitoring of electrical apparatus located in explosive risk environments for partial discharge is often omitted.
It is an object of embodiments of the present invention to address these issues.